* Commission calls for 40 pct carbon emission cut by 2030
* Plan sees 27 pct green energy goal, no national targets
* Proposals update current targets to fight climate change
* Environmental groups say EU has pulled back on ambitions (Adds details, reaction)
By Charlie Dunmore
BRUSSELS, Jan 22 (Reuters) - The European Union scaled back its long-term climate and energy ambitions on Wednesday, proposing less stringent targets than in the past, because of tougher economic conditions and the need to curb rising energy costs.
The European Commission - the bloc's executive - said EU governments should face a single binding target to reduce carbon dioxide emissions by 2030 to a volume that is 40 percent lower than 1990 levels.
That represents a doubling of the goal in the existing 2020 target, but it is still below what some scientists and environmentalists say is needed to prevent the worst effects of climate change and is less than some policymakers wanted.
"What we are presenting today is both ambitious and affordable," Commission President Jose Manuel Barroso told a news conference in Brussels as the goals were unveiled.
The Commission' 2030 strategy statement reflects a new sense of pragmatism at a time when European growth is slow and the EU's biggest trading partners, including the United States, Japan and Canada, have scaled back their climate commitments.
Beyond the headline goal, the Commission also scaled back its demands on member states when it comes to adopting renewable sources of energy such as solar and wind power.
Current national targets require countries to ensure renewables account for 20 percent of total EU energy use by 2020. But after that date, binding national targets will be scrapped.
Instead, the Commission is recommending an EU-wide goal of "at least 27 percent" renewables, a higher level but without the hard and fast national targets currently in force.
That would allow Britain and others to meet their emissions targets by building nuclear power plants, which are carbon-free but not renewable. Generous government subsidies designed to meet the 20 percent renewables target have been blamed for pushing up energy costs.
"The aid systems for renewable energy have not always been cost-efficient. In some places we have promoted renewable energy, but it has cost too much," the bloc's energy commissioner, Guenther Oettinger, said.
Conscious of how far Europe now lags the United States when it comes to shale gas, the Commission also decided not to put obstacles in the way of shale exploration. That could allow Poland and others to reduce their reliance on coal, which emits around twice as much carbon as gas.
The U.S. shale boom has resulted in gas prices of about a third of those in Europe.
Global talks to try to agree on a successor to the 1997 Kyoto Protocol, the first and only international agreement to tackle climate change, are due to be held in Paris next year.
Environmental campaigners said the Commission's plans amounted to a weakening of Europe's climate ambitions.
"The European Commission is gambling with our future. The proposed 40 percent target would scupper any hopes of keeping temperatures below the 2 degree danger level," Lies Craeynest of campaign group Oxfam said in a statement.
Scientists say a rise of more than 2 degrees Celsius (3.6 Fahrenheit) would lead to catastrophic effects, including a sharp rise in sea levels.
EU leaders are due to debate the 2030 goals at summits in March and June, ahead of formal legislative proposals expected early next year.
These would still require lengthy debate by EU governments and the European Parliament before becoming law, and Barroso warned that agreement on the Commission's proposed targets was far from assured.
"I think it is possible to come to an agreement on 40 percent. I think it's not going to be easy, and there will be more pressure to put it down than to put it up, I can promise you," Barroso said.
The one firm legislative proposal included in Wednesday's announcement was a scheme to prop up Europe's faltering carbon emissions trading market, with the aim of removing carbon permits from circulation to support prices.
Under the proposal, the Commission would set aside up to 12 percent of carbon permits from 2021, as long as certain conditions are met. Among the conditions is that the number of allowances to be set aside must exceed 100 million. (Additional reporting by Nina Chestney in London; Editing by Luke Baker and Jane Baird)